The present invention relates to pillow block assemblies and more specifically to a novel external device for selectively converting a pillow block from a "free" to "held" unit or from a "held" to a "free" unit.
The term "free" as used herein shall refer to a pillow block arrangement wherein the bearing assembly has limited axial movement or displacement relative to the pillow block and the term "held" shall mean a unit wherein the bearing assembly is fixed against at least axial displacement in the pillow block. Pillow blocks are typically used to rotatably mount journals or the like and in most instances are used in at least pairs for rotatably supporting a large unit mounted for rotation between the pillow blocks in the manner illustrated, for example, in FIG. 1.
FIGS. 2 and 3 show a conventional pillow block assembly including means for converting the pillow block from a free to a held unit.
Typically the pillow block comprises a housing A having a cylindrical internal seat or cavity B for a bearing assembly C consisting usually of an inner ring D mounted on a shaft or journal E and an outer ring F mounted in the seat in the pillow block housing. The bearing has labyrinth seals G at opposite axial ends and a pair of retaining rings H which as illustrated in FIG. 2 are spaced apart an axial distance greater than the length of the outer ring to allow for limited axial movement of the bearing assembly in the pillow block.
In most installations involving a plurality of pillow blocks, assembly requirements and variable operating conditions dictate that at least one of the pillow blocks be a free unit and the other a held unit. For example, in an installation such as that illustrated in FIG. 1, the combination of a held and free unit allows for axial movement of the bearing assembly in the free unit to compensate for expansion due, for example, to temperature variations. At present most suppliers of this type of equipment provide two distinct pillow block assemblies, a free unit of the type illustrated in FIG. 2 and a held unit of the type illustrated in FIG. 3. The held unit includes a stabilizing ring J disposed between one of the retaining rings and the axial end face of the outer ring of the bearing. These units are supplied as complete assemblies, lubricated at the factory ready for assembly on the shaft. As a practical matter, it has been found that conversion from free to a held unit or vice versa is impractical since it usually requires destruction of the outer seal. Conversion also runs the risk of contaminating the lubricant in the unit.
A further drawback is the fact that separate inventories are required which adds to the overall cost of manufacture.